Rapid formation of intermetallic joints through ultrasonic-assisted die bonding with Sn–0.7Cu solder for high temperature packaging application

[Display omitted] Rapid formation of complete intermetallic-phases (IPs)-composed joints during die bonding for high temperature applications was achieved by pressureless and fluxless ultrasonic-assisted soldering in air within seconds. The joint consisted of sole (Cu,Ni)6Sn5 plus a thin layer of Cu3Sn possessed a rather low thermal resistance of 0.252mm2KW−1 and a high shear strength of 69MPa. This rapid formation of fully IPs-composed structures was probably accelerated by ultrasonic cavitation and streaming effects through supersaturation of copper in the melted solder. Compared with transient-liquid-phase soldering, this method dramatically reduces the processing time and there was no external force acted on the dies.